Expose scroll customization for touch to JS (behind REF).

Source/core/page/scrolling/ScrollStateCallback.cpp

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "core/page/scrolling/ScrollStateCallback.h"
+
+namespace blink {
+
+NativeScrollBehavior ScrollStateCallback::toNativeScrollBehavior(String nativeScrollBehavior)
+{
+    DEFINE_STATIC_LOCAL(const String, disable, ("disable-native-scroll"));
+    DEFINE_STATIC_LOCAL(const String, before, ("perform-before-native-scroll"));
+    DEFINE_STATIC_LOCAL(const String, after, ("perform-after-native-scroll"));
+
+    if (nativeScrollBehavior == disable)
+        return NativeScrollBehavior::DisableNativeScroll;
+    if (nativeScrollBehavior == before)
+        return NativeScrollBehavior::PerformBeforeNativeScroll;
+    if (nativeScrollBehavior == after)
+        return NativeScrollBehavior::PerformAfterNativeScroll;
+
+    ASSERT_NOT_REACHED();
+    return NativeScrollBehavior::DisableNativeScroll;
+}
+
+} // namespace blink